1. The Field of the Invention
The present invention relates to an engagement chain. More particularly, the present invention relates to driving device which uses an engagement chain to drive articles forward and backward in parallel with a set surface. Such hoisting and lowering devices may be used as production facilities in various kinds of production fields, transfer facilities in the transportation field, care facilities in the medical welfare field, stage facilities in the art field, and the like.
2. The Relevant Technology
One example of a driving device is a so called chuck chain, which hoists and lowers articles, such as heavy articles, using a pair of engagement chains, which are integrally formed with the device, and which are used to lift and lower the articles, while being engaged with each other, such as the chain described in Japanese Patent Publication No. JP-3370928, which is shown in FIG. 1.
In a conventional engagement chains currently known in the art, such as the engagement chain 500 shown in FIG. 9, various modifications to the shape of hook 552 formed in respective link plates 550, the pitch between pins, the pitch between bushes and the like, have been made. Despite these variations, however, most engagement chains continued to use the same shape for the buckling limiting flat surface 551 formed on the opposite side of the hook surface. As shown in FIG. 9, most form plate shapes are formed so a space is produced between adjoining buckling limiting flat surfaces 551 when a pair of engagement chains 500 are engaged with each other.
One problem with the conventional engagement chain 500, however, is that a compression force between link plates 550, or a relative shift between link plates opposed to each other may occur along the above-mentioned bucking limiting flat surface 551 because of the space generated between the bucking limiting flat surfaces 551. Furthermore, the space between the buckling limiting flat surfaces 551 reduces the rigidity of a pair of engagement chains 500 engaged with each other. This results in reduced buckling strength in the combined engagement chains 500.
One solution to the reduced buckling strength, is to reduce the influence by not forming a space between buckling limiting flat surfaces 551, such as when the engagement chain 500 is used in a driving device in a floor setting form, which is uses a floor surface as a setting surface, as described in the Japanese Patent Publication No. 3370928. However, when the engagement chain 500 is used in a driving device using a suspended form which uses a ceiling surface as a setting surface or in a driving device in a cantilever supporting form which uses a vertical wall surface as a setting surface, the problem can become significant.
Accordingly, there is a need for an engagement chain which solves these conventional problems by providing an engagement chain which has an improved buckling strength when two segments of the engagement chain are engaged with each other without blocking engagement operations between inner tooth plates and between outer tooth plates. Further, there is a need for an engagement chain which has reduced working load on molding of inner tooth plates and outer tooth plates while reliably maintaining the chain engagement position of the engaged segments of the engagement chain, even if the engaged segments are used a driving device in a suspended form, which uses a ceiling surface as a setting surface, or a driving device in a cantilever supporting form, which uses a vertical wall surface as a setting surface.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced